JPS593562B2 - Multifilament yarn manufacturing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Entangled, twisted, self-adhesive, fine fiber multifilament yarns using thermoplastic resins can be made by melt flow multifilament yarn manufacturing techniques.

This technique extrudes thermoplastic resin into a gas stream through a die with an annular die opening, thins the extruded thread to form a cone-shaped stream of fibers in the space, and converts the fibers into multifilament threads. Form by collecting.

This method produces many unique products with different properties due to differences in fiber collection methods.

One embodiment of the invention is useful as a cigarette filter.

Most thermoplastics are extruded to make fibers.

For example, polypropylene fibers are subjected to conventional melt spinning followed by stretching, crimping, twisting, texturing, etc. to produce the final desired shape of the polypropylene fibers.

The purpose of the method of the present invention is to continuously convert thermoplastic resins such as polypropylene into entangled, twisted and self-adhesive fine fiber multifilament yarns by melt-blown multifilament yarn manufacturing techniques.

One embodiment of the present invention has an average bulk density of 0.05 to 0.
．． A multifilament yarn of 20 &fiL of intertwined fine polypropylene fibers is provided.

This is useful as a filter material, especially as a cigarette filter.

Multifilament threads of polypropylene fibers used in cigarette filters do not need to be wrapped with filter paper, and can be made by simply cutting them and wrapping them with the paper on the outside of the cigarette.

The present invention relates to extruding thermoplastic resins into fine fiber multifilament yarns by extruding the resin through a die having an annular array of die openings.

A gas flow, preferably air, is provided by concentric slotted gas conduits inside and outside the die opening ring to attenuate the extruded resin into fine fibers.

Preferably, the die is provided with a die opening ring so that the thermoplastic resin can be extruded to form a cone of fibers in the space in front of the die opening.

This cone is largest near the die and tapers toward a virtual focal point in front of the die.

Changing the virtual focal length of the fiber cone in front of the die by adjusting the relative velocity of the gas flow exiting from the inner and outer guide holes of the die opening ring, thereby changing the shape of the fiber cone formed in the space. Can be done.

The conical profile of the fibers emerging from the die opening is further adjusted by supplying an auxiliary gas flow through a gas conduit in the form of a jet in the center of the die opening ring.

The auxiliary gas flow helps cool the fibers prior to collection and also alters fiber adhesion.

The auxiliary gas stream is therefore used to change the conical shape of the fibers as they exit the die and attenuate, so that the profile of the fibers in space becomes more cylindrical in the deposition area.

By adjusting the auxiliary gas flow in this manner, the time and temperature history of the extruded resin as well as the deposition mode of the individual fibers can be varied.

Fibers can be collected as multifilament yarns in several different ways.

Fibers may be collected by moving the multifilament thread of fibers toward the front of the die or through the center of the die opening ring.

Here, the method of moving the multifilament yarn in front of the die and collecting it is defined as forward take-out, and the method of moving the multifilament yarn of the fiber in the opposite direction and collecting it through the center of the die opening ring is defined as reverse take-out. By distinguishing the direction of movement of multifilament yarns of fibers.

Depending on the direction in which the multifilament yarn is moved and collected, distinctly different products can be produced.

For example, in reverse withdrawal a smooth skin of bonded fibers is created on the outside of the multifilament yarn, while in forward withdrawal a relatively soft outer layer of individual fibers or fiber aggregates is created on the multifilament yarn.

Fixed or rotating collection members may be used in the deposition area to collect the fine fibers in the desired shape.

The recommended collection member is a stabilizing bar.

Preferably, the stabilizing rod is rotated to produce a uniform multifilament yarn.

Rotation of the stabilizing bar creates a permanent twist in the product and also avoids the formation of holes or soft centers in the multifilament yarns due to removal from the stabilizing bar.

However, if a hollow multifilament thread is desired, a large fixed or rotating rod can be used.

Furthermore, by using more than one die, multifilament yarns of intertwined, twisted, and self-bonded fibers can be modified.

Thus, by passing the multifilament yarn through one or more dies and using the multifilament yarn instead of a stabilizing bar as a collecting member on which to collect further fibers, additional fibers can be added to the outside of the multifilament yarn. Fibers can be bonded together.

The direction in which the multifilament yarn passes through the die opening ring of each die determines the overall properties of the multifilament yarn.

In one embodiment of the invention, a multifilament yarn of intertwined, twisted and bonded thermoplastic fibers consisting of a multiplicity of essentially continuous thermoplastic fibers having an average diameter of 2 to 40 microns is created, as described above. The fibers run essentially individually and independently of adjacent fibers in a fairly uniform manner from a point near the center of the multifilament yarn to a point near the outer surface of the multifilament yarn. Forms loops arranged in a certain direction.

The fibers of the cylindrical multifilament yarn are preferably self-adhered and a smooth skin of the adhered fibers is on the outer surface of the multifilament yarn.

In FIG. 1, which shows an embodiment of the general melt-blown multifilament yarn production process, a thermoplastic resin, such as polypropylene, is introduced into a feed hopper 1 of an extruder 2.

The thermoplastic resin is heated in an extruder 2 and driven by a drive device 3.
The extruder 2 is placed under shear by a screw (not shown) in an extruder 2 driven by.

The thermoplastic resin is extruded into a gas stream through a die 4 having a number of die openings 5 arranged in an annular manner.

The gas flow is provided by gas conduit holes 6 and 7 arranged concentrically inside and outside the circumference of the die opening 5, respectively.

The thermoplastic resin is extruded from a die 4 as continuous fibers,
The fibers are attenuated by the gas flow exiting through the guide holes 6 and 7.

Gas is supplied to the ports 6 and 7 by lines 8 and 9, respectively.

Each of lines 8 and 9 can be adjusted independently with respect to pressure and temperature (not shown).

By adjusting the gas flow, the extruded fibers are tapered out of the die opening into a conical shape, with the largest part of the cone being near the die opening 5.

Attachment area 1 near the virtual apex of the cone of attenuated fibers
Collect the fibers at 0.

The distance from the die opening 5 to the deposition area 10 is largely controlled by the relative gas velocities exiting the guide holes 6 and 7.

The finely shredded fibers are collected on a collection member 11.

Collection members come in a variety of shapes and sizes.

The collection member 11 is preferably a stabilizing rod 12, which can be fixed or rotating.

Stabilizer bar 12 passes through the center of funnel 13 or other device.

The device 13 serves as a support for stabilizing the bar 12 when rotated by the drive device 14.

The funnel 13 also prevents fine fibers that miss the target from reaching the drive 14.

As the fibers gather on the stabilizing rod 12, they intertwine and adhere to each other.

When collecting the fibers in the deposition area 10 on the stabilizing rod 12,
In order to change the shape of the fibers, an auxiliary gas flow is provided through gas inlets 15 made in double-walled pipe 16.

The double-walled pipe 16 is located along the central axis of the die 4 and an axis formed within the annulus of the die opening 5.

The gas flow exiting the gas conduit 15 is directed towards the collecting member 11 or the stabilizing rod 12, and the air flow changes the adhesion of the fibers in the attachment area 10 so that the fibers become more cylindrical.

Gas, preferably air, is supplied to the double-walled pipe 16 by a line 17, which line is regulated with respect to pressure and temperature.

An auxiliary gas flow can be used to change the time and temperature course of the fibers as well as the shape and entanglement of the fibers.

The gas supplied through the gas guide hole 15 is supplied through the gas guide holes 6 and 7.
The air supplied through can be of different temperatures.

To begin the melt-blown multifilament yarn operation,
In both forward and reverse withdrawals, the starter bar 18 is extended into the attachment zone 10 along the stabilizing bar 12 in order to draw the fibers from the stabilizing bar 12 as a continuous multifilament thread.

FIG. 1 illustrates reverse extraction. As shown in FIG. 1, the starter rod 18 is pulled through the center of the double-walled pipe 16 to attach the multifilament yarn to a take-up reel 19 driven by a motor 20.

2 and 3 show details of the die 4 used in the present invention.

The die 4 includes a die assembly 21, and the die assembly is connected to the extruder 2.
It has multiple passageways from the inlet to the annular polymer distribution chamber 22 and to the die opening 5.

The die 4 has a toroidal shape. By "toricoid" we mean any cross-sectional die assembly that rotates about an axis, in which case the die openings 5 of the die 4 are arranged annularly about the axis.

Die assembly 21 consists of an inner ring member 23 and an outer ring member 24 that meet at a surface 25.

To create a passageway from the annular polymer chamber 22 to the die opening 5, a number of grooves 26 are formed in the inner ring member 23, the outer ring member 24, or both surfaces.

The outer cover 27 covering the outer ring 24 defines an outer gas conduit 7, the outlet of which is in the form of a concentric slot outside the die opening 5.

The inner cover 28 defines an inner gas conduit 6, the outlet of which is in the form of a concentric slot inside the die opening 5.

The thermoplastic polymer is introduced into the polymer inlet 29, forced into the annular polymer chamber 22, and extruded through the die opening 5.

Hot gas, preferably air, is supplied by lines 8 and 9;
The pressurized gas is supplied to the gas introduction ports 30 and 31, and the pressurized gas is supplied from the gas introduction ports to the outer gas introduction hole 7 and the inner gas introduction hole 6, respectively.

The conical shape of the attenuated fibers extruded from the die opening 5 of the die 4 is controlled by the die geometry and the relative velocity of the gases coming from the gas inlets 6 and 1.

The gas conduits 6 and 7 are made in the die 4 such that the angle α between the two conduit outlets or slots 32 and 33 is up to 90°, preferably between 077° and 60°.

The plurality of passages or grooves 26 in die assembly 21 define an angle β that is less than angle α and between the angles defined by gas conduit holes 6 and 7.

Preferably the angle β is within the angle defined by the gas inlets 6 and 7.

Furthermore, the center line of the die opening 5 or the groove 26 and the axis of the die 4 are 0.
The die geometry is dimensioned to form an angle Δ varying from 20° to 60°, preferably from 20° to 60°.

The die geometry influences the shape of the cone of the fiber as it exits the die opening 5, but this shape changes immediately with the relative velocity of the gases coming from the gas conduits 6 and 7, so that the die opening 5 The angle γ between the exiting fiber and the axis of the die is Oo
It may lie in the range from 90° to 90°, preferably from 20° to 60°.

The collection of fibers in the deposition area 10 is more fully illustrated in FIG.

The melt-blown multifilament yarn operation of the present invention can produce a myriad of products by varying the conditions of the deposition area 10.

The fiber is extruded from the die opening 5 and becomes thinner, initially forming a cone A.
It becomes the shape of

As the fibers converge, the individual fibers come into contact with each other and with the already formed multifilament yarn.

The fibers can become sticky or self-adhesive because they are hot and begin to intertwine.

However, as the fibers thin, they continue to stick to each other and to the multifilament yarns in the attachment area 10 far from the die opening, eventually forming a mass of entangled, twisted, and self-adhesive fibers.

The deposition area 10 is the black cloth furthest from the die opening where the fibers gather from the point where the fibers first contact occurs into a mass of fibers as a multifilament yarn.

The attachment area 10 is several inches to about 1 foot (30 cIrL) away from the die opening 5.

It is possible to vary the angle γ of the extruded thermoplastic resin independently, and by means of an auxiliary gas flow exiting the guide holes 15, as well as to vary the deposition area 10 depending on the direction of withdrawal.

In most cases, the use of an auxiliary gas flow exiting from the inlet 15
The fibers are deposited more evenly, thus creating a multifilament yarn with more uniform fibers.

When the multifilament yarn 34 is removed from the attachment area 10 by reverse withdrawal as shown in FIG. 4, the multifilament yarn 34 has a bonded smooth outer surface; When removed from the container, the outer surface has a more fuzzy appearance.

By placing the attachment area 10 further away from the die opening 5, multifilament yarns with lower density and less self-adhesion can be produced.

FIG. 5 shows a melt blown multifilament yarn technique using multiple dies.

By using two or more dies, multifilament yarns with a variety of unique properties can be produced.

Extruder 7L81 for thermoplastic resins such as polypropylene
and 91 into hoppers 70, 80 and 90, respectively.

Extrude resin from dia 2, 82 and 92.

As shown, in the first die 2, a stabilizing rod 73 is rotated by a motor 74 to produce a multifilament yarn 75 using forward extraction and passed through a double-walled pipe 83 along the axis of the die 82.

Further fibers are attached to the outside of the multifilament yarn 75 to create a larger multifilament yarn 84.

The multifilament yarn 84 passes through a protection device 85.

The die 82 is also operated with front extraction.

Multifilament yarn 84 then passes through a double-walled pipe 93 that runs along the axis of die 92 .

The operation of die 92 is reverse ejection so that a smooth bonded fiber skin is created on the outer surface of multifilament yarn 94.

Multifilament yarn 94 is wound onto a reel (not shown).

Although the three dies 2, 82, and 92 are illustrated as two forward exits followed by one reverse exit, when using more than one die, the combinations that are possible as the number of dies used increases. Of course, this will increase.

In Figures 6 and 7, looping of two single fibers is illustrated for both forward and reverse withdrawal to illustrate the general properties of multifilament yarns made with melt-blown multifilament yarn technology.

Of course, because of the large number of fibers involved, there is some entanglement and some adhesion between the fibers, so that the continuous looping of the outer surface fabric from the centerline of the multifilament yarn is not necessarily perfect.

However, when a multifilament yarn made by melt-blown multifilament yarn technology is pulled and cut, the multifilament yarn is cut substantially along the lines shown as loops to provide a cone and conical socket cut.

In certain applications, melt-blown polypropylene multifilament threads make good filters for cigarettes.

The invention will be explained in more detail by the following examples.

The following example illustrates the operation of the melt blown multifilament yarn manufacturing technique according to the present invention.

All samples were made using polypropylene resin with a melt flow rate of 30.

Example 1 The following multifilament yarns were made by reverse drawing under the conditions shown in the following table.

When the product was cut into short segments, it exhibited a uniform appearance in the center with a thin, soft, adherent skin.

When tested as a cigarette filter, it showed results equivalent to or better than Winston cigarette filters in terms of total amount of solids removed.

Example 2 Die temperature is 680'F (360°C), air temperature is 680'F (360°C)
73500 by reverse extraction at 0'F (360℃)
I made denier multifilament yarn.

The primary air velocity is 1.6 #/min (72 #/min).
6fl/min), auxiliary air flow rate 1.2#/min (5449
/min), and the polymer flow rate was 16.9 I/min.

The free end of a 1/16 inch (16 m) diameter stabilizer rod was located at a distance of 8 inches (20 crrL) from the die.

The tip of the stabilizing rod is 1/4 inch (6M) x 9 inch (22
, 9 cm).

The barrier was set to 20 for the rotation of the stabilizer bar.

To heat seal the surface, the formed multifilament yarn is 1 to 6 feet (30 to 184 cIrL)7
The sample was drawn through a die heated to 275° C. at a rate of 1 minute.

The die has a short tapered inlet with a 9/32 inch (7 m) channel and a 1 inch (2,2 m) channel at the exit.
It had a long length of 5 CIIL).

The refined product, when recovered at a speed of 6 feet (184 crrL) and 7 minutes, was a solid rod consisting of a dense rope-like, fibrous core and a compact, shiny surface.

Once again at low speeds the surface became a solid plastic tube.

The rods could be cut cleanly with a razor blade and had adequate filtration action.

Example 3 Various hollow cylindrical fiber materials were made by appropriate design of stabilizing rods.

The die and primary air are below 670°~680° (354~36
It was operated at a polymer flow rate of 12-20 g/min at a temperature of 0°C).

Primary and auxiliary air flow rates were adjusted to obtain stable operation.

3/8 inch (1 (1771) or 1/2
An inch (1,3 CrrL) diameter tube was rotated.

A large funnel tapering toward the die was attached coaxially with the tube.

Move the funnel 6 to 15 inches from the die (15 to 38 cf.
rL) and the apparatus was operated with the tube tip 0-12 inches (0-30 crn) away from the die.

The apparatus was rotated at 50-1100 rpm to continuously draw hollow cylindrical fibers from the center of the die.

The product has a diameter of 5/8 inches to 1y2 inches (1.6 to 3.
It had a bulky cylindrical shape with a diameter of 3/16 inch to 1 inch (511g1. to 1.3CrIL) and a generally circular center hole.

Under certain operating conditions, a dense fibrous skin covered the outer surface.

The product exhibited elasticity after being pressed and exhibited considerable stiffness along its longitudinal axis.

This product is useful as a cartridge filter (for sealing the fused end) or as a slip-on insulator.

Example 4 A multifilament yarn was made using the forward extraction method.

Later, the multifilament yarn was drawn to create a twisted yarn.

The die is at 665'F (352°C) and the primary air is at 684
(362°C), respectively, and the polymer flow rate was increased to 1.
The speed was set at 1.5.9/min.

The stabilizing rod had a 3/8 inch (9M) wide by 1 inch (2.5 crrL) long blade at its end and extended 15 inches (38 crfL) in front of the die.

Rotate the stabilizing rod at 17QQrpm and continuously rotate 20,00
A 0 denier multifilament yarn was pulled out.

Then the multifilament yarn is 4 feet (122cr
rL) 7 minutes into a 325'F (163°C) oven and stretched 4/1.

The product is a fairly stiff twisted thread, with 1
．． It exhibited a strength of 8117 denier and a breaking strength of 15%.

Using a die with 240 die openings on a circumference of 4 inches (10.2 cIIL) in diameter, polypropylene could be made into multifilament yarn under the following operating conditions.

Suitable operating range die temperature ″F ('C) 600-700 (3
16-351) Air temperature ″F (°C) 60
0-750 (316-399) Polymer flow rate g/Gan rL
8+-25+primary air flow rate #7 cod, 65-3.
6+ Auxiliary air flow rate #7in O-<2+ Distance from the free end of the stabilizing rod to the die in, (CrrL) Reverse extraction 0-15 (0-38) Front extraction 6
-30 (15-76) PM Reverse extraction 0-200 or more Forward extraction 0-1800 or more Product extraction speed, ft (α/mm) In the tables, the numbers do not imply absolute limits.

Some numbers are marked with a plus (+) sign to indicate the limitations of the particular machine used to obtain them.

Any other numerical values merely state suitable operating conditions and are not intended to identify hard limits.

Furthermore, it is expected that the operable range for operating conditions will change when changing die dimensions and using different equipment accordingly.

Examples 5 to 9 Polypropylene (melt flow rate 30) produced by reverse extraction in an apparatus similar to that shown in FIG. 1 using a die having 240 die openings on a circumference of 4 inches (10.2 fi) in diameter was melt-blown.

The formed multifilament yarn was cut and tested as a cigarette filter.

The cut filter product was compared to a commercially available filter made of cellulose acetate.

The specific conditions used in making the multifilament yarns and specific multifilament yarn products are shown in Table 1 below.

Comparing Examples 5 and 6, the high pressure drop through the filter or multifilament yarn product and the high percentage of tar removal indicate the effect of fiber size in the multifilament yarn.

The high air flow rate and low polymer flow rate in Example 5 forms thinner fibers resulting in higher ΔP and more controlled tar removal.

In both Examples 5 and 6, the total denier of the filter products was approximately 50,000.

Examples 7 and 8 demonstrated the effect of fiber size in a filter product having a denier of about 60,000.

In Example 8, fine fibers were formed.

Example 9 shows one example of the most suitable conditions for obtaining cigarette filter material.

Lower ΔP and higher tar removal rates were obtained in this example compared to commercially available filters made with cellulose acetate.

The properties of the multifilament yarn can be varied by controlling the rotation of the stabilizing rod in the melt blowing process.

The rotation of the stabilizing rod forms a helical twist in the multifilament yarn.

This twist can be expressed in revolutions per unit length.

Multifilament yarn is 0.02 to 0.8 per inch
A uniformly well packed multifilament yarn can be obtained when it has a twist of rotation (0.05 to 2 turns per cm).

When the multifilament yarn has few kinks or the number of revolutions per unit length is approximately 0, the structure of the multifilament yarn is loose and often non-uniform.

A rigid and uniform multifilament yarn structure can be obtained at around 0.5 revolutions per inch (1.3 revolutions per cIIL).

When the revolutions per inch (crrL) approaches 1 (2,5), the multifilament structure is too rigid and too tight for use as a cigarette filter material.

Furthermore, the number of revolutions per inch (CrrL) is 1 (2,5
) or above tends to produce a product that is very hard in the center and has a loose outer surface and no kinks.

Thus, the uniformity of the twist in the multifilament yarn is completely lost as the rotation of the stabilizing rod increases.

Although this is highly undesirable in producing multifilament yarns for cigarette filters, such an effect may be desirable in filter materials intended for other applications.

In short, the twists that form part of the multifilament yarn are related to the uniformity of the cross section of the multifilament yarn.

The surface properties may vary and therefore the end use of the multifilament yarn product may also vary.

When manufacturing multifilament yarns for cigarette filters, the appropriate external surface characteristics include a flexible bonded web-like surface to create a small, stiff filter.

A multifilament yarn having such a flexible bonded web-like surface can be cut into an appropriate length for a filter without changing its properties as a multifilament yarn.

Multifilament yarns with soft, unbonded exterior surfaces tend to be fluffy and lack the stiffness necessary for cigarette filter applications.

Furthermore, when cutting soft or unbonded multifilament yarns, the cut ends are damaged.

If the external surface of the multifilament yarn has clumps of fused fibers forming a rough skin, the resulting filter product will be too textured, uneven, and hard, and will crack when the filter material is cut. will occur.

The properties of the external surface of the multifilament yarn are generally controlled by the distance between the inner circumference of the die opening and the attachment area, i.e. by controlling the angle at which the extruded fiber reaches the point of contact with the multifilament yarn. can be obtained.

If the extruded fibers are collected in the deposition area very close to the die opening, the outer surface of the multifilament yarn will have a surface consisting of fused fibers.

On the other hand, if the fibers are collected in a deposition zone that is too far from the die opening, the external surface of the multifilament yarn will be frizzy and uneven because the fibers are not bonded.

In the examples shown in Table 1, a smooth, uniform external surface was obtained using the reverse extraction method.

The properties of the multifilament yarn obtained according to the present invention will be further described.

Figures 6 and 7 illustrate fiber deposition during reverse and forward withdrawal.

Although this illustration is highly simplified, it does display the general characteristics of multifilament yarns.

The large number of fibers extruded from a die by the melt-blowing process produces a multifilament (considerable tangles and self-adhesion of the fibers during the manufacturing process).

However, in FIGS. 6 and 7 the general characteristics of the multifilament yarn of the present invention are shown.

That is, it is a point that is 1 inch (2,5 crrL) to 20 inches (50,8 crrL) in length from a point on the axis or more distant from a point radially off-axis or outside the multifilament yarn. This is an operation to form a loop shape that is repeatedly formed toward the surface.

As illustrated in FIGS. 6 and 7, in the case of reverse extraction (FIG. 6), the point of contact as the continuous fibers come to form part of the overall multifilament yarn structure is a radially distal point. In the case of forward extraction (FIG. 7), the point of contact is on the axis or at a point radially close to the axis.

However, in either case, when the multifilament yarn formed by reverse extraction or forward extraction is pulled by the tension generated along its axis, it generally breaks along the line of the fibers forming the loop, resulting in a conical fracture. will occur.

Another feature of the multifilament yarn of the present invention is that the diameter of the fibers forming the multifilament yarn structure is much smaller than fibers previously used in the production of multifilament yarn products.

The average fiber diameter of multifilament yarn products made according to the invention is as small as 2 to 40 microns.

In addition to polypropylene, various types of nylon (666 and 66
10), polystyrene, polyethylene terephthalate,
Thermoplastic resins such as polymethyl methacrylate and even polyolefins such as polyethylene, ethylene-propylene copolymers, etc. may be used.

By using a partitioned die, or when using more than one die, one or more thermoplastic resins can be used in the melt blown multifilament yarn manufacturing method of the present invention.

Thus, multifilament yarn properties can be varied by using mixtures of thermoplastic resins, and multilayer multifilament yarns can be formed from different resins.

Furthermore, additives or binders can be added into the multifilament yarn by blowing out one or more air streams.

In this way, products of composite structure with special desirable properties, such as charcoal-impregnated filter rods, can be formed.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing the entire method for producing melt-blown multifilament yarn by reverse extraction, Fig. 2 is a detailed cross-sectional view of the die, partially broken away, and Fig. 3 is a detailed view of the inner tubular member of the die. Figure 4 is an enlarged view of the die showing the attachment area;
The figure is a schematic diagram of a melt-blown multifilament yarn production method using a plurality of dies, FIG. 6 is a schematic diagram showing the attachment of fibers during reverse take-off, and FIG. 7 is a schematic diagram showing the attachment of fibers during forward take-out. 4...Die, 5...Die opening, 6,7
...Gas introduction hole, 10...Adhesion area, 1
1...Recovery member, 12...Stabilizing rod, 2
2...Annular polymer distribution chamber, 29...
Polymer introducer

Claims (1)

[Scope of Claims] A multifilament yarn made of a plurality of substantially continuous thermoplastic fibers having an average diameter of 12 to 40 microns entangled, twisted, and bonded, wherein the thermoplastic fibers are sufficiently uniform. In this state, from a point close to the center of the multifilament yarn to a point closer to the outer surface of the multifilament yarn, adjacent fibers go back and forth almost individually, forming loops arranged in a generally constant direction. An apparatus for producing a multifilament yarn, comprising: (1) a die assembly defining a plurality of passages communicating with a polymer inlet and a die opening ring, located concentrically with the die opening ring; an annular ring for melt blowing thermoplastic resin containing a member defining an outer gas conduit hole immediately outside the ring, and a member defining an inner gas conduit concentric with the die opening ring and immediately inside said ring; (ii) a collection member rotated by a driving device and concentric with the annular die and the two annular gas guide holes, at one end of which is a collection member of a fiber cone melt-blown from the die; An apparatus comprising: a collection member having a collection portion located at a virtual focal point; and (iii) a take-up reel for winding up the fibers on the collection member.